2A1 Air-dry moisture content

Use this method when it is necessary to correct soil chemical results based on air-dry samples to an oven-dry basis.

When the air-dry moisture content (M%) is known, the correction from air-dry result to oven-dry result is as follows:

Apparatus

• Calibrated laboratory oven, fan-forced and set at 105°C.
• Moisture tins (with lids) of known weight.
• Desiccator.

Procedure

Confirm the weight of each clean, dry, weighing container (W₁ g). Weigh accurately from 10 to 50 g air-dry soil (<2 mm) into each container and record weight (W₂ g). With lids removed, dry at 105°C to constant weight then quickly transfer to a dry desiccator (no desiccant) to cool. When cool, replace relevant lids and reweigh (W₃ g) to determine weight of moisture [(W₂ – W₁) – (W₃ – W₁)] = W₄ g.

Discard soil on completion in a responsible manner.

Calculation

Report as air-dry moisture content (%).